1 ///////////////////////////////////////////////////////////////////////////////
2 /// \file pop_back.hpp
3 /// Proto callables Fusion pop_back
4 //
5 //  Copyright 2010 Eric Niebler. Distributed under the Boost
6 //  Software License, Version 1.0. (See accompanying file
7 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8 
9 #ifndef BOOST_PROTO_FUNCTIONAL_FUSION_POP_BACK_HPP_EAN_11_27_2010
10 #define BOOST_PROTO_FUNCTIONAL_FUSION_POP_BACK_HPP_EAN_11_27_2010
11 
12 #include <boost/fusion/include/begin.hpp>
13 #include <boost/fusion/include/end.hpp>
14 #include <boost/fusion/include/prior.hpp>
15 #include <boost/fusion/include/pop_back.hpp>
16 #include <boost/proto/proto_fwd.hpp>
17 
18 namespace boost { namespace proto { namespace functional
19 {
20     /// \brief A PolymorphicFunctionObject type that invokes the
21     /// \c fusion::pop_back() algorithm on its argument.
22     ///
23     /// A PolymorphicFunctionObject type that invokes the
24     /// \c fusion::pop_back() algorithm on its argument.
25     struct pop_back
26     {
27         BOOST_PROTO_CALLABLE()
28 
29         template<typename Sig>
30         struct result;
31 
32         template<typename This, typename Seq>
33         struct result<This(Seq)>
34           : result<This(Seq const &)>
35         {};
36 
37         template<typename This, typename Seq>
38         struct result<This(Seq &)>
39           : fusion::result_of::pop_back<Seq>
40         {};
41 
42         template<typename Seq>
43         typename fusion::result_of::pop_back<Seq>::type
operator ()boost::proto::functional::pop_back44         operator ()(Seq &seq) const
45         {
46             // Work around a const-correctness issue in Fusion
47             typedef typename fusion::result_of::pop_back<Seq>::type result_type;
48             return result_type(fusion::begin(seq), fusion::prior(fusion::end(seq)));
49         }
50 
51         template<typename Seq>
52         typename fusion::result_of::pop_back<Seq const>::type
operator ()boost::proto::functional::pop_back53         operator ()(Seq const &seq) const
54         {
55             return fusion::pop_back(seq);
56         }
57     };
58 }}}
59 
60 #endif
61